initial value

related perks

modifies

initial value

related perks

related traits

Any damage taken is reduced by this amount. Damage Resistance can be increased by wearing armor.

”— Fallout In-game description

Damage Resistance (DR) is a derived statistic in the SPECIAL character system.

Any damage taken is reduced by a percentage based either completely or in part in this number, depending on the game. Damage Resistance can be increased by wearing armor, or by taking certain chems or perks, depending on the game.

Contents

In the original Fallout games, DR (Damage Resistance) is one of three stats by which a character can reduce or avoid damage. The other stats are AC (Armor Class) and DT (Damage Threshold). DR occupies the "final step" for combat and simulates the effect of how armor can help diffuse the energy of a bullet and reduce its lethality (like real-life Kevlar armor).

More specifically, after AC is checked for a successful hit and after DT is checked to reduce the damage, if there is any incoming damage, DR applies:

While DT can completely negate damage done, DR cannot. As the equation suggests, DR is capped at 90%, and any damage that goes past DT has a minimum of 1.

The maximum Damage Resistance is 85%, regardless whether this value is obtained by armor, perks, drugs or a combination of these. This makes the effects of Nerd Rage! and Med-X somewhat less useful, as even without chems, the Lone Wanderer can permanently gain up to 94% Damage Resistance through equipment and perks (with The Pitt additional content). The T-51b power armor and the Enclave Hellfire power armor plus their respective helmets have a max DR of 60. Combined with the five permanent perks (34%) gives the maximum DR without drugs or having less than 20 percent of your hitpoints. Without the additional content you would still be able to obtain a maximum DR of 91% with power armor. Note that these numbers assume a fully repaired suit of armor, which, when the T-51b armor is actually being worn, is only possible if the player boosts Crazy Wolfgang's repair skill to 100 by reverse pickpocketing workman's coveralls from Point Lookout onto him because there is only one copy of this armor and it can only be repaired by non-player characters. Enclave Hellfire armor can be found, but it is rare (only obtainable with Broken Steel loaded). For players who prefer non-power armor, you can still obtain a permanent DR of 82% (79% without The Pitt add-on) with ranger battle armor, ghoul mask, the ranger battle helmet and the perks listed below.

Replace the hockey mask above with Poplar's hood which has 2 lower DR than the hockey mask but can be worn with the ghoul mask producing 5 DR rather than 4. This combination repairs the Agility damage (+2 small guns, +2 sneak, +2 Action Points), adds +10 sneak, permanent 74% DR, +40 Action Points and feral ghouls will not become hostile. It is a possibility for those who have not yet found the hockey mask, or missed acquiring it altogether. This option, however, excludes obtaining the Barkskin perk which offers 5 DR itself.

Damage Resistance is applied before damage threshold, contrary to the original Fallout games. So, for a character with 30 DR and 20 DT (i.e. a NCR Veteran Ranger), an attack that deals 80 damage is first reduced by 30% (leaving 56 damage), then the damage threshold is subtracted from that number, leaving a final damage of 36. As a result of this, a high damage resistance has a very large effect on a character's ability to withstand damage. For full damage formula see Fallout: New Vegas combat.

The only pieces of equipment in the game that raise DR instead of DT are:

In addition, DR can be conferred via the console by entering player.forceAV DamageResist xx where xx is between 0 and 85. Values beyond 85 are ignored by the game; 85 is the maximum DR, a likely holdover in the game engine from Fallout 3.

A rare few non-player character characters have perks which grant them DR in addition to the DT from their armor. These include:

Damage resistance returns in Fallout 4. However, the stat is no longer a 1-1 relationship with actual % damage reduced, as its value can be in excess of 1,000 on certain models of power armor.

Instead, the amount of damage reduction the Sole Survivor gets out of the damage resistance is actually based on how much potential weapon damage is coming in; unlike previous games, net damage reduction is based on a ratio between the potential weapon damage done and the damage resistance, with diminishing returns for high damage resistance.

The amount of damage reduced by damage resistance climbs very quickly until damage resistance is about half of the potential weapon damage, after which diminishing returns means one gets less and less damage reduction per point of damage resistance. If damage resistance is exactly equal to the potential weapon damage done, then exactly half of the damage is negated. In other words, if one has 50 ballistic damage resistance and is shot by an enemy doing 50 ballistic damage, then they will receive 25 damage.

The most important factor is the ratio between damage resistance and potential weapon damage:

WeaponDamage

Resistance

FinalDamage

ReductionPercent

50

0

49.5

1%

50

10

45

10%

50

25

32

36%

50

50

25

50%

50

100

19

61%

50

250

14

72%

50

1000

8

83%

The upshot is that unlike previous games, it is very hard to get to the point where enemy damage is reduced to the range of ~20% or less. In addition, because the ratio between damage resistance and weapon damage is so important and because damage reduction grows very quickly at first for low values of the ratio, a higher damage resistance pays off mostly because it gives the player character better damage reduction against more-damaging attacks, not necessarily because it gives them better damage reduction against the same, weaker attack as before.

In other words, going from 20 to 40 damage resistance will only further reduce the damage done from a 10-damage shot by about ~12% (~61% to ~69% damage reduction), but it will dramatically boost the player character's damage reduction against a 100-damage grenade by about 23% (~10% to ~30% damage reduction). However, significant mitigation against such high damage is harder to achieve, since it is harder to get enough damage resistance to generate an appreciably high resistance-to-damage ratio. In otherwords, getting a 5-1 ratio is easy against a 20 damage shot, but very difficult (essentially limited to power armor) against a 100 damage grenade.

This is applied after the ratio and exponent are calculated, so damage resistance is applied on the base potential weapon damage, before difficulty-based multipliers are included in. This means that damage resistance is the same level of effectiveness (or ineffectiveness) on every difficulty level.

Companions are unmodified. On all difficulty levels they do 1x damage and take 1x damage from enemies. This means that companions generally become a bit more effective at higher difficulty levels since they will generally be taking less damage and doing more damage than the player character.

Regardless of where one hits an enemy/are hit by an enemy, the total damage resistance of all currently equipped pieces of armor is used for the formula.

The actual damage reduction formula is:

where default game settings are:

fPhysicalDamageFactor = 0.15

fPhysicalArmorDmgReductionExp = 0.365

This is a coefficient (multiplier) for the net damage done, not the actual damage reduction; so lower numbers are better (more damage is negated).

If one wants the actual % damage reduction simply do

Damage done as function of the damage to armor ratio.

Damage mitigation as function of the armor to damage ratio.

There are variations on this DamageCoeff calculation based on weapon used:

Projectile and close combat weapons use PaperDamage (essentially, the number one sees in the Pip-Boy), RangeMultiplier, and PowerAttackMultiplier for the damage part.

Energy weapons use WeaponBaseDamage and RangeMultiplier for the damage part (essentially, they are more vulnerable to their respective damage resistance).

WeaponBaseDamage is affected by weapon mods and is e.g. doubled with a 2x charged laser musket

RangeMulti is 1.0 at 100% WeaponRange or closer, 0.5 at 200% of WeaponRange or farther, and scales from 1.0 to 0.5 as range increases from 100% to 200% of WeaponRange.

Poison deals damage each second, as a distinctly inflicted hit, typically for 10 seconds; for example, if the player character has a poison resistance of 5 and suffers a poison 3 hit, then once per second for 10 seconds, they will suffer a 3 damage hit, resisted with a resistance of 5, which otherwise follows the rules for projectile damage.

Bleeding works like poison, except that there is no such thing as bleeding resistance. Even robots such as 2nd generation synths and sentry bots will take bleeding damage, as it is a general damage over time effect.

Radiation damage has two subtypes. Almost all of it in the game is poisoning; each point of radiation poisoning from a radiation "hit" is resisted by radiation resistance (as per the energy damage resistance formula), and resolves as a .1% loss of maximum HP for each point that gets through. The only perk that raises radiation poisoning damage inflicted by a weapon is Nuclear Physicist, and radiation immunity makes a target ignore radiation poisoning entirely.

Non-poisoning radiation damage follows the normal rules for energy damage, including modification by perks; it ignores radiation immunity, and creatures with radiation immunity typically have no radiation resistance.

Explosive modifies other damage types - for example, something can inflict explosive energy damage. Explosive damage uses the same formula as the underlying type, but is affected by additional perks and effects that interact with explosives. Padded and dense armor mods reduce the damage taken by 25% for padded and 50% for dense from explosion base damage. E.g. a dense armor mod reduces the damage taken from a frag grenade by 75 ( 150 * 0.5) in addition to normal physical resistance.

When something has multiple resistible damage types (ballistic, energy, radiation and poison are the currently resistible types, with any of them capable of being explosive or not, and radiation can be poisoning or not - almost all radiation sources are poisoning), one "hit" resolves as a hit for each damage type applied. Likewise, when something deals both direct and area of effect damage, a target is hit by each one individually. For example, if one removes the Lorenzo's Artifact gun mod from the original gun and attaches it to an Irradiated Gamma gun with an Electric signal carrier antennae, a charged shot from the weapon will inflict 5 distinct "hits": radiation poisoning, radiation damage, explosive radiation poisoning, explosive radiation damage and explosive projectile damage.

Due to the way the damage formula works, the 40% armor piercing of some weapons mods actually result in a flat +20% effective damage done, on any foe, regardless of the weapon base damage or the DR of the target.